1. Field of the Invention
The present invention relates to a photographic film cassette, more particularly to a film cassette in which scratches on the photographic film due to dust, or the like, is prevented.
2. Description of the Related Art
It is known to utilize a 35 mm film cassette having a film leader which does not protrude from the cassette shell prior to loading, and which is thus easily loaded in a camera. Such a device is disclosed in Japanese Patent Laid-open Publications Nos. 1-306844 and 1-306845. Rotation of a spool, by a mechanism in the camera, in the direction of unwinding the photographic film, causes the film leader to advance to the outside of the cassette shell through a film passage mouth. The cassette shell is provided with a device for preventing the roll of film from loosening when the spool is rotated. Accordingly, the rotary force of the spool is transmitted to the film leader.
In such a leader-propelling type film cassette, the cassette shell is molded from plastics or the like, as it has a complicated structure. The photographic film is then likely to be scratched by roughness on the surface of the plastic. When the photographic film exposed in the camera, dust, dirt, or the like, situated in the camera, might adhere to the photographic film and thus be drawn into the cassette shell with the photographic film upon rewinding.
When the exposed photographic film is propelled for the purpose of development, the film leader abuts on and is separated by a separating claw formed in the cassette shell. It is often necessary to rotate the roll of film a plurality of times in the cassette shell before completely separating the film leader. Therefore, a rather large amount of motion of the photographic film within the cassette shell is required as compared to a cassette shell of a conventional film cassette. When dust is situated between film surfaces and the inside surfaces of the cassette shell scratches often are formed on the film surfaces.